mole Definition

mole¹
noun

1. A small insectivorous burrowing mammal with velvety greyish-black fur, a naked muzzle, very small eyes and strong front legs with very broad feet adapted for digging.
2. colloq
A spy who works inside an organization and passes secret information to people outside it.

Etymology: 20c in sense 2; 14c in sense 1.

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mole²
noun

1. A raised or flat, dark, permanent spot on the skin, caused by a concentration of melanin. Technical equivalent naevus. See also freckle.

Etymology: Anglo-Saxon mal.

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mole³
noun

1. pathol.medicine.
An abnormal fleshy mass formed in the uterus.

Etymology: 17c: from French môle, from Latin moles mass.

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mole⁴
noun

1. chem.
(symbol mol) the SI unit of amount of substance, equal to the amount of a substance (in grams) that contains as many atoms, molecules, etc, as there are atoms of carbon in 12 grams of the isotope carbon-12.

Derivative: molal
adj

Said of a solution: containing one mole of dissolved substance per kilogram of solvent.

Derivative: molar

Belonging or relating to a mole.

Per mole or per unit amount of substance.

Etymology: Early 20c: from German Mol, from Molekül molecule.

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mole⁵
noun

1. A pier, causeway or breakwater made of stone.
2. A harbour protected by any of these.

Etymology: 16c: from Latin moles mass.